Hey! That's it. This is WATERLESS hand cleaner. You don't need a sink! Anyone can clean up (and be reasonably fresh smelling) BEFORE they come into the house!
The ad above isn't quite there yet, though. No drama. Make it a dirty bathroom towel? So,
Oh, you expected big finish to this? Nawww. We could go on and eventually find the perfect answer. If I did, I probably wouldn't post it here... not first, anyway.
In advertising it's the marketplace (and, sigh, the budget and deadline) that decides how this creative process ends. So in any case, there's more to it than sketches and brainstorming.
In fact, the conceptual process never really ends. Weaker ideas get replaced, and good ones get developed further. (Only a few campaigns are so strong they can run virtually forever, and even then, the market changes.)
And as I hope I've illustrated, good ideas can be developed further before the campaign begins. It's finished, but it isn't. That may be the only thing that advertising has in common with fine art.
How would you develop that last one? (That's a rhetorical challenge... Please enjoy it to yourself.)